The present invention relates to a hydrostatically operated continuously variable transmission including a swash-plate-type axial-piston hydraulic pump and a swash-plate-type axial-piston hydraulic motor which are coupled in a closed hydraulic circuit, the hydraulic pump and motor having pump and motor cylinders, respectively, which are disposed coaxially with each other, the swash plate of at least one of the hydraulic pump and the hydraulic motor being tiltable.
Hydrostatically operated continuously variable transmissions are known in the art as disclosed in Japanese Patent Publication No. 32-7159, for example.
In the conventional hydrostatically operated continuously variable transmission, a pump cylinder and a motor cylinder are relatively rotatably disposed in confronting relationship with a hydraulic pressure distributor interposed therebetween, and input and output shafts are coupled respectively to the pump and motor cylinders at their centers. Therefore, the axial length, particularly, of the transmission is quite large. The transmission may not be employed in some applications dependent on the layout of the power unit with which the transmission is to be combined. For instance, a transmission for use in an automotive power unit generally has an input shaft to be coupled coaxially with the crankshaft of the engine of the power unit. If such a transmission comprises a conventional hydrostatically operated continuously variable transmission, then the overall length of the power unit is increased to the extent that the power unit may not be installed in the limited space of an engine compartment.